Why am I getting the wrong result when using float? [duplicate]

Question

Possible Duplicates:
Why is (double)0.6f > (double)(6/10f)?
Why is floating point arithmetic in C# imprecise?

I have the following code in C#:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace StackOverflow
{
    class Program
    {
        static void Main(string[] args)
        {
            float num1 = 17.03F;
            float num2 = 17F;
            float result = num1 - num2;
            Console.WriteLine(result);
        }
    }
}

The code works fine but I am not getting the expected result. Can someone explain why this is happening?

Your expectations of floating point arithmetic are incorrect. See the question linked from the comment above, or any number of other questions tagged floating-point. Also see csharpindepth.com/Articles/General/FloatingPoint.aspx — Jon Skeet
– Jon Skeet, Commented Nov 11, 2010 at 9:22
What result are you expecting and what result are you getting? — Michael
– Michael, Commented Nov 11, 2010 at 9:22
@Jon, both questions have the wrong names, thus - low search relevance. — Alex
– Alex, Commented Nov 11, 2010 at 9:23

Øyvind Bråthen · Accepted Answer · 2010-11-11 09:22:52Z

4

I guess you are refering to deviations cause by Floating point arithmetics. You can read about in in the provided link.

If you really need to make the calculation 100% accurate, you can use decimal instead of float.

answered Nov 11, 2010 at 9:22

Øyvind Bråthen

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Comments

Alex · Accepted Answer · 2010-11-11 09:22:04Z

1

Because you are using float. Float is an extremely approximate value. Always use it with an Epsilon (maximum error allowance) when comparing.

I am guessing you are getting result = 0.02999999?

answered Nov 11, 2010 at 9:22

Alex

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Comments

Paddy · Accepted Answer · 2010-11-11 09:22:30Z

1

Floating point maths is likely to contain rounding approximations, see the many duplicate questions on this site, or read here:

http://en.wikipedia.org/wiki/Floating_point

answered Nov 11, 2010 at 9:22

Paddy

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alanc · Accepted Answer · 2012-10-13 04:51:43Z

1

What about this? : What Every Computer Scientist Should Know About Floating-Point Arithmetic

edited Oct 13, 2012 at 4:51

alanc

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answered Nov 11, 2010 at 9:25

alpha-mouse

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